There is a continuing need in various industrial arts such as the electrical electronics, automotive, and appliance industries for injection molding compounds which have improved crystallization properties.
It is well known to those skilled in the art that glass fiber reinforced poly(1,4-cyclohexylenedimethylene terephthalate) molding compositions crystallize rapidly when injection molded using mold temperatures greater than 150.degree. C. At temperatures of greater than 150.degree. C., oil heated molds are usually used. However, some molders only have the capability of heating molds to temperatures of 80.degree. to 120.degree. C. using hot water or steam. Therefore, it is necessary to add a crystallization aid to the glass fiber reinforced poly(1,4-cyclohexylene-dimethylene) terephthalate compositions so that rapid crystallization can occur at mold temperatures significantly less than 150.degree. C.
Low molecular weight aliphatic polyesters can be used as crystallization aids. However, there is commonly a breakdown in the molecular weight of the poly(1,4-cyclohexylenedimethylene) terephthalate that occurs with the use of these low molecular weight aliphatic polyesters as crystallization aids.
It is a distinct advantage, therefore, to formulate reinforced molding compositions based on poly(1,4-cyclohexylenedimethylene) terephthalate comprising a low molecular weight aliphatic polyester which allows for rapid crystallization at mold temperatures of significantly less than 150.degree. C. without the usual breakdown in the molecular weight of the poly(1,4-cyclohexylenedimethylene) terephthalate.
U.S. Pat. No. 3,565,852 discloses the use of polyesters with melting points less than or equal to 150.degree. C. with at least partial aliphatic character as crystallization aids for poly(ethylene terephthalate)(PET) only.
European patent application 0,387,398, published on Sept. 19, 1990 discloses the use of aliphatic polyesters as crystallization aids for PET only. This application discloses that aliphatic polyesters react with PET.
U.S. Pat. No. 4,223,113 discloses the use of oligomeric aliphatic polyesters as crystallization aids for poly(alkylene terephthalates). The aliphatic polyesters used are based on acids(C1-C20) and diols (C2-C20). The oligomeric aliphatic polyesters used in this work can have a maximum molecular weight of 6000. These polyesters are disclosed as being useful in poly(alkylene terephthalates).
There is a need in the art to find new reinforced poly(1,4-cyclohexylenedimethylene) terephthalate compositions wherein rapid crystallization can occur at mold temperatures significantly less than 150.degree. C. without the usual breakdown in the molecular weight of the poly(1,4-cyclohexylenedimethylene) terephthalate.